Fix bug #7422 "order by" doesn't work

Field with wrong buffer was used to make sort key, which results in producing
same sort key for all records.

mysql-test/r/view.result

@@ -1726,3 +1726,17 @@ sum(a)
 drop procedure p1;
 drop view v1;
 drop table t1;
+CREATE TABLE t1(a char(2) primary key, b char(2));
+CREATE TABLE t2(a char(2), b char(2), index i(a));
+INSERT INTO t1 VALUES ('a','1'), ('b','2');
+INSERT INTO t2 VALUES ('a','5'), ('a','6'), ('b','5'), ('b','6');
+CREATE VIEW v1 AS
+SELECT t1.b as c, t2.b as d FROM t1,t2 WHERE t1.a=t2.a;
+SELECT d, c FROM v1 ORDER BY d;
+d	c
+5	1
+5	2
+6	1
+6	2
+DROP VIEW v1;
+DROP TABLE t1, t2;

mysql-test/t/view.test

@@ -1569,3 +1569,15 @@ drop procedure p1;
 drop view v1;
 drop table t1;
 
+#
+# Bug#7422 "order by" doesn't work
+#
+CREATE TABLE t1(a char(2) primary key, b char(2));
+CREATE TABLE t2(a char(2), b char(2), index i(a));
+INSERT INTO t1 VALUES ('a','1'), ('b','2');
+INSERT INTO t2 VALUES ('a','5'), ('a','6'), ('b','5'), ('b','6');
+CREATE VIEW v1 AS
+  SELECT t1.b as c, t2.b as d FROM t1,t2 WHERE t1.a=t2.a;
+SELECT d, c FROM v1 ORDER BY d;
+DROP VIEW v1;
+DROP TABLE t1, t2;

sql/filesort.cc

@@ -631,7 +631,7 @@ static void make_sortkey(register SORTPARAM *param,
 	    *to++=1;
 	  /* All item->str() to use some extra byte for end null.. */
 	  String tmp((char*) to,sort_field->length+4,cs);
-	  String *res=item->val_str(&tmp);
+          String *res= item->str_result(&tmp);
 	  if (!res)
 	  {
 	    if (maybe_null)
@@ -673,8 +673,8 @@ static void make_sortkey(register SORTPARAM *param,
 	}
       case INT_RESULT:
 	{
-	  longlong value=item->val_int();
-	  if (maybe_null)
+          longlong value= item->val_int_result();
+          if (maybe_null)
           {
 	    *to++=1;				/* purecov: inspected */
             if (item->null_value)
@@ -715,7 +715,7 @@ static void make_sortkey(register SORTPARAM *param,
 	}
       case DECIMAL_RESULT:
         {
-          my_decimal dec_buf, *dec_val= item->val_decimal(&dec_buf);
+          my_decimal dec_buf, *dec_val= item->val_decimal_result(&dec_buf);
           if (maybe_null)
           {
             if (item->null_value)
@@ -733,7 +733,7 @@ static void make_sortkey(register SORTPARAM *param,
         }
       case REAL_RESULT:
 	{
-	  double value= item->val_real();
+          double value= item->val_result();
 	  if (maybe_null)
           {
             if (item->null_value)